Several changes:

    - remove WValidator::fixUp() (#2807)
    - fix #2821 segfault while cancelling a resource continuation
    - fix #2826 libwtdbmysql install dir
Several changes:

    - fix for SingleThreadedApplication to handle external application events properly
    - WFileupload::setFilters documentaion
    - fix WTableView bootstrap 2 selection offset problem (#2812)
tighten up Wt::Dbo template externing
Several changes:

    - fix setFirstFocus typo (#2870)
    - fix bootstrap WNavigationBar responsive problems (#2813)
    - fix cn, ru homepage (#2866)
    - added a WSortFilterProxyModel::invalidate() method
    - make WTemplate resilient against widgets being removed during rendering
    - remove C++11 constexpr idea for WFormModel fields (#2852)
    - patch from Bruce: do not parse 'f' and 't' values as an exception (#2841)
fix redundant layout touches during measurement
Several changes:

    - amend Dbo test cases to try to reproduce #2831
    - documentation and widget gallery updates, #1754
    - fix WMediaPlayer::play() + other changes timing issue (#2819)
    - Wt::Dbo: reorganizations from Oracle backend branch
    - added WLineEdit::setInputMask()
Several changes:

    - Dbo: fix firebird backend regressions
    - Dbo postgres: support timezone columns (from Bruce Toll) #2840
Recent versions of Debian (and thus, Ubuntu) install freetype.h to
/usr/include/freetype2/freetype.h

This change makes CMake find freetype.h, while still maintaining
compatibility with systems which install it under e. g.

  /usr/include/freetype2/freetype/freetype.h, or
  /usr/include/freetype/freetype.h